I had another thought, though it might be a bit late.
Tahu- Fire (duh)
Lewa- Vegitation
Gali- Water
Kopaka- Ice
Onua- OG Earth+Stone
Pohatu- Wind.
While the previous environments would be self explanatory, Pohatu is a bit different. His environment could be a sweeping prarie, and his power of wind gives him incredible foot speed.
Lewa would stay mostly the same, save for any forms of powered flight. He could continue being the most agile of the bunch.